Gas mixture ratio dependence of ion temperature in ECR plasma

The ion temperature in N2/Ar and O2/Ar electron cyclotron resonance (ECR) plasma is measured by high-resolution optical emission spectroscopy for pressure of 0.27 Pa and microwave power of 2.4 kW. It is found that as the nitrogen gas concentration is increased, the ion temperature in N2/Ar ECR plasma decreases drastically and the uniformity of the radial electron density distribution improves. It is considered that the decrease of the ion temperature in N2/Ar ECR plasma is caused by the decrease of the radial electric field. In the case of O2/Ar ECR plasma, the ion temperature increases as the oxygen gas concentration is increased. It is considered that the increase of the ion temperature in O2/Ar ECR plasma is caused by energy exchange between electrons and ions because the electron temperature considerably increases with increasing of the oxygen concentration.